Arrangements in which applications installed on computers control and/or monitor the subscribers on communication systems are known as CTI systems (CTI=Computer Telephony Integration). In these arrangements a telephony server, often also termed a CTI server, is connected between the applications and a communication system. There is here a data connection between each communication system and the CTI server as well as a data connection in each case between the various applications and the CTI server. The applications thus do not communicate directly with the communication systems, but with the aid of a CTI server. One often also refers to third-party CTI systems.
The subscribers connected to the communication systems are differentiated from one another on the basis of identification codes. One common identification code here is the extension number, which is always unambiguous for the subscribers of an individual communication system, i.e. exactly one subscriber is assigned to each extension number. Incidentally, this applies not only to subscribers in the traditional sense, that is to say to telephone lines, but also to central office lines, announcement ports, collective lines and the like. The general term ‘resource’ is used to refer to all these subscribers.
For the control and/or monitoring of resources by applications, messages are transmitted between the applications and the communication system on which the respective resource is being operated. An important part of the messages is always the identification code of the respective resource in order to be able to assign the correct resource to the message, both from the communication system and from the application. The identification code assigned to a resource is also often termed the resource ID (ID=identification). If a plurality of communication systems are connected to a CTI server, the CTI server uses the resource ID to forward a message sent by the application to the particular communication system to which the respective resource is connected. In the reverse direction the CTI server transmits the messages coming from the communication systems to the particular application or to all the applications provided for access to the respective resource. The assignments can be configured in the CTI server. Since the messages of various communication systems are brought together in the CTI server and are transmitted over a single data connection to the respective application or applications, from the point of view of the application this results in a “one system image”, i.e. the applications do not differentiate whether the various resources are connected to a single communication system or to various communication systems. Each application differentiates the resources solely on the basis of the resource ID. Since the resource ID is frequently identical to the extension number of the corresponding connection to the communication system, performance of the control and/or monitoring, “call control”, is also referred to as “line-based”.
On the existing systems it has proved disadvantageous that when controlling and/or monitoring resources of a plurality of communication systems, the resource IDs must be unambiguous not only with respect to a single communication system, but with respect to all communication systems to which such resources are connected. If the resource IDs are formed as usual from the extension numbers, all resources, that is to say also all subscribers of the CTI system, must have unambiguous extension numbers. In CTI systems for communication networks having a plurality of communication systems and having many subscribers, this results in unmanageably long extension numbers.